JPH079645A - Polyester sheet for thermoforming - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a polyester sheet for thermoforming, which has excellent heat-sealing property, does not cause blocking in a wound state, and can be smoothly released from the stacked state of the molded body. To do. [Composition] On the inner surface of the amorphous linear saturated polyester resin layer 2 which is a base layer, a blended resin 1 with a copolyester having a glass transition temperature of 85 ° C. or lower, or another type of polyester containing the polyester is heated. A polybutylene terephthalate 3 is compounded on the outer surface of the layer opposite to the layer 1 with the heat seal layer for the purpose of preventing blocking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a polyester molded lid or container which holds a flavor component having contents such as food and has low temperature heat sealability in a package filled with food or the like. For polyester sheet for thermoforming.

[0002]

2. Description of the Related Art Conventionally, a polyester container, which is one of the adherends to be covered in a package filled with food or the like, has been widely used as the container for food or the like.

[0003]

This is a polyester formed by a thermoforming method such as vacuum forming or pressure forming when the lid material and the container are sealed by the heat sealing method after filling the contents. Due to the characteristics of polyester, the molded lid, container, and the like are excellent in retaining the taste of foods, and thus are often used recently, but they have a problem in heat sealability.

Therefore, for the purpose of imparting low-temperature heat-sealing properties to the heat-sealing layer, studies have been made on low-temperature heat-sealing by using a copolymer type polyester having a low glass transition point or a blend of the polyesters.

However, such a polyester sheet has a defect that the innermost heat-sealing layer surface and the polyester layer surface of the base layer are likely to cause blocking in a wound state of the sheet, and is wound at the time of thermoforming such as vacuum forming or pressure forming. Even when the molded articles cannot be taken out, or even when the thermoformed molded articles are stacked, the individual molded articles are blocked when filling and heat-sealing the contents such as foods, which causes a problem that the mold cannot be released.

As a means for preventing blocking, a method of applying a solution such as a silicone resin as a release agent on the surface of the base layer has been attempted. However, such means involves heating the release agent in a wound state. There is a drawback that heat sealability is greatly impaired by adhesion or migration to the seal layer surface.

The present invention is excellent in heat sealability and
It is an object of the present invention to provide a thermoforming polyester sheet which does not cause blocking in a wound state and can be smoothly released from the stacked state of the molded body.

[0008]

Means for Solving the Problems The means of the present invention for achieving the above-mentioned object is to compound polybutylene terephthalate having a melting point of 180 ° C. or higher on the outer surface of an amorphous linear saturated polyester resin layer of a base layer. And the combined thickness is
A thickness of 10 to 50 μm is suitable.

The compounding method is an embodiment in which dry lamination of a polybutylene terephthalate film with a urethane adhesive or the like or coextrusion sheeting is used.

[0010]

The present invention configured as described above has the following operations.

First made of heat-sealable polyester
A layer and an amorphous linear saturated polyester resin layer serving as a base layer as a second layer adjacent to the first layer, and a polybutylene terephthalate layer as a third layer adjacent to the layer. Thereby, as described above, the anti-blocking property at the time of winding and the anti-blocking property of the stacked molded body can be obtained.

[0012]

EXAMPLE An example of the thermoforming polyester sheet of the present invention will now be described with reference to the drawings.

FIG. 1 shows a three-layer coextrusion sheet A according to an embodiment of the present invention.
The configuration of the first layer 1 and the second layer 2 is shown.
And a third layer 3.

In the figure, the first layer is heat-sealable polyester.

The thickness of the first layer 1 is preferably 15 μm or less.

In order to obtain the polyester which is the first layer 1 having such suitable physical properties, the inventors of the present invention have conducted extensive studies and as a result, have found that the amorphous wire having good heat-sealing property and elongation at break close to zero. Amorphous linear saturated polyester with very low glass transition temperature, which can be well adapted to this purpose, for the purpose of improving heat sealability in a fused state with the target polyester to be adhered It has been found that the object can be achieved by blending polyester.

The blended polyester is, for example, as a heat-sealable amorphous linear saturated polyester, a registered trademark Ko manufactured by Eastman Kodak Company.
dabond Copolyester 5116 (glass transition temperature 58 ℃) or
DuPont Selar PT X-207 (glass transition temperature 71 ℃)
And the amorphous linear saturated polyester with extremely low glass transition temperature, registered trademark Byron GM-900 (glass transition temperature -20 ° C) manufactured by Toyobo Co., Ltd. are properly blended to obtain the desired physical properties. To be

The blend ratio of the amorphous linear saturated polyester having a low glass transition temperature is 30% or less, preferably 15 to
A range of 25% is suitable.

As the blending method, a blending mixer which is generally used in the art can be used, and before being fed into an extruder for film formation, it is necessary to prevent hydrolysis required for general polyester extrusion. Dehumidifying and drying for is essential.

In FIG. 1, the second layer 2 serves as a base layer of the polyester sheet for thermoforming of the present invention, and the amorphous linear saturated polyester resin is, for example, ethylene glycol, propylene glycol, or one of glycol components. Condensation polymers of alcohol components such as those having 1,4-cyclohexanedimethanol substituted with dicarboxylic acids such as terephthalic acid and isophthalic acid are used. Generally, amorphous polyethylene terephthalate is mainly used. In general, a glass transition temperature of 70 ° C. or higher is used.

The thickness of the layer depends on the shape of the molding and, in particular, the drawing ratio of the molding, and is generally from 200 μm to
A thickness of 1000 μm is used as a thermoforming polyester sheet.

For the purpose of improving the gas barrier property, a polyethylene vinyl alcohol resin or a polyvinylidene chloride resin layer, which is widely used in the art, is formed between the first layer 1 and the second layer 2. I don't mind.

The third layer 3 of the embodiment of the present invention prevents blocking of the thermoforming polyester sheet comprising the first, second and first layers claimed in the present invention, and
The object could be achieved by compounding the third layer with polybutylene terephthalate, which also has recyclability by appropriately compatibilizing each layer without impairing the heat sealability and thermoformability. Is.

A suitable thickness of the layer is 10 to 50 μm. As a composite method, dry lamination of a polybutylene terephthalate film with a urethane adhesive or coextrusion sheeting can be used.

Regarding the polybutylene terephthalate type of the layer, the homo type is superior to the polybutylene terephthalate copolyester type in the anti-blocking property in the constitution of the present invention.

Examples of the polybutylene terephthalate which are suitable for the purpose include, for example, Duranex registered trademark manufactured by Polyplastics Co., Ltd. and NOVADUR registered trademark manufactured by Mitsubishi Kasei Co., Ltd., which has a melting point of 224 ° C.

In the present embodiment, the extrusion temperature of the sheet made of the first to third layers prepared by the coextrusion sheeting method is set to 230 ° C. for the first layer, 240 ° C. for the second layer and 260 ° C. for the third layer. I went.

Examples 1 to 7 are shown in Table 1, and Comparative Examples 1 to 4 are shown in Table 2.

According to Table 1, the anti-blocking property is
Clearly good results are shown in the examples of the invention.

As shown in FIG. 2, the blocking property of the take-up roll is such that the inner surface and the outer surface of the sheet A are different when they are applied to the thermoforming machine 4 such as vacuum forming and pressure forming, and when the sheet winding 5 is unwound. If it is blocked, the sheet A cannot be unwound.

Therefore, in the figure, the polyester sheet of the present invention is smoothly unwound and the sheet A is softened by the infrared heaters 7, 7 arranged on both sides of the polyester sheet. , A step of forming the molded body b by the pressing force of the plug 9.

Next, the molded body b is filled with contents such as food and is put on a loose cup filling and sealing machine 11 which is heat-sealed with the lid member 10. As shown in FIG. A large number of molded bodies b stacked on 12 are released one by one, and to a molded body receiving bucket 13 provided at the lower part thereof,
In the case where the molded articles b are fitted one after another and the molded article b and the molded article b that are adjacent to each other overlap in the storage body 12 and block, the operation cannot be performed.

In the figure, the molded bodies b thermoformed by the sheet A of the present invention are smoothly separated one by one from the lower one in a stacked state in the storage body 12, Fitted in bucket 13,
The inside of the molded body b is filled with the contents by the filling machine 14, and in the next step, the lid material 10 is continuously fed from the lid material winding 15.
To the molded body b of the bucket 13 and heat-sealed between the lid member 10 and the flange portion of the molded body b by the heat seal bars 16 and 16, and thereafter, unnecessary end portions of the lid member 10 are cut by a cutter. A package 18 punched and packaged at 17 is shown.

In FIG. 4, the lid member 10 thermoformed by the sheet A of the present invention is heat-sealed with the polyester container 19.

FIG. 5 shows the case where the sheet A is thermoformed into the molded body b which is the container as described above.

[0036]

[Table 1]

[0037]

[Table 2]

Polyester sheet for thermoforming Outer layer: Polybutylene terephthalate registered trademark Duranex, 600FP (melting point 224 ° C.) Base layer: Polyethylene terephthalate resin J-025 (Glass transition point 70 ° C.) manufactured by Mitsui Pet Resin Co., Ltd. Inner layer: A: Coester polyester manufactured by Eastman Chemical Co., Ltd. Kodabond Copolyester 5116 (glass transition 58 ° C.) B: Polyester registered trademark Byron GM9 manufactured by Toyobo Co., Ltd.
00 (glass transition point -20 ° C, melting point 113 ° C).

Seal strength Biaxially stretched nylon film 15 μm thickness / same as above Kodabond C
180 ° C × 2.0 kg between opolyester 5116, 50 μm thick and inner surface
30 in Tensilon after heat sealing at / cm ² × 1.0 seconds
Measured at 0 mm / min, CH.S.

Anti-blocking property Both the take-up roll and the molded body / molded body were observed at 40 ° C. × 24 hours, and after sufficiently cooling at 23 ° C., the degree of blocking was observed.

Judgment ☆: No blocking ○: Very little blocking, no hindrance to production Δ: Medium blocking, hindrance to production ×: Large blocking, cannot be released.

[0042]

The thus obtained polyester sheet for thermoforming of the present invention is excellent in anti-blocking property, so that it is excellent in productivity such as thermoforming, and is also produced during filling and sealing of a molded body. In addition to excellent heat resistance and heat sealability, it is also useful in terms of recyclability after the role of the package is completed.

In addition to the food field, it can be used in a wide range of fields such as medical fields and electronic parts fields.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing a part of the configuration of an embodiment of a thermoforming polyester sheet according to the present invention.

FIG. 2 is an explanatory view showing a molding process of a molded body using the sheet of FIG.

FIG. 3 is an explanatory view showing a process of molding a package containing contents by the molded product molded in FIG.

FIG. 4 is a cross-sectional view showing a heat-sealed state of a packaging body of an example in which the sheet in FIG. 1 is adopted as a lid material.

5 is a cross-sectional view showing a package heat-sealed state of an example in which the sheet in FIG. 1 is adopted as a container.

[Explanation of symbols]

 1 Polyester 2 Amorphous Linear Saturated Polyester Resin 3 Polybutylene Terephthalate

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[Procedure amendment]

[Submission date] June 30, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

The present invention provides a polyester sheet for thermoforming, which has excellent heat-sealing properties, does not cause blocking in the wound state, and can be smoothly released from the stacked state of the molded body. With the goal.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29L 9:00

Claims (1)

[Claims] 1. A blend resin with a copolyester having a glass transition temperature of 85 ° C. or lower, or another type of polyester containing the polyester is heated on the inner surface of an amorphous linear saturated polyester resin layer as a base layer. A polyester sheet for thermoforming, which is provided as a seal layer, and is a composite of polybutylene terephthalate and the heat seal layer on the outer surface of the layer opposite to the layer for the purpose of preventing blocking.